The present invention relates generally to digital peak detection and more specifically to digital peak detection circuitry and acquisition mode that is usable in a measurement test instrument, such as an oscilloscope.
High speed digital measurement instruments, such as oscilloscopes, digitizers, and the like, use interleaved acquisition pipes for acquiring digitized samples of an input signal in an acquisition channel. A common sample clock is used to drive circuitry in each pipe with each pipe's sample clock being delayed from the other pipes' sample clocks. Each pipe has a track-and-hold that samples the incoming signal, an analog-to digital converter that digitizes the analog sample, and a demultiplexer that decimates the digitized samples at a user selected acquisition rate. The decimated digitized acquisition samples from each pipe are interleaved and stored in memory for display and/or further processing. The interleaved stored samples provide a maximum channel acquisition rate that is effectively N times greater than the sample clock rate where N is the number of acquisition pipes.
The TDS 700 Series Oscilloscopes, manufactured and sold by Tektronix, Inc., Wilsonville, Oreg., and assignee of the present invention, include a digital peak detect acquisition mode that is used during slow acquisitions to detect high-speed events occurring between regular acquisition samples. During digital peak detect, one of the acquisition pipes acquires samples at the maximum sample rate of the pipe and accumulate a minimum value and a maximum value of the high speed samples over the period of the slower requested acquisition rate. The minimum and maximum values over each acquisition interval are stored in memory for display. This method is limited to capturing events with a duration that is greater than or equal to the sampling rate of the acquisition pipe.
What is needed is an apparatus and method for acquiring shorter duration events during the digital peak detection acquisition function.